The problem with Google Chat in this context is that even history-off Chats are kept for at least 24 hours before being destroyed (I’ve sometimes seen longer due to caching), so a record is created and then destroyed. That isn’t allowed when an obligation to preserve the record exists.
I admit I don’t know whether something like un-logged IRC would be allowed, but at the very least, any IRC clients that do log the history even for the purpose of displaying it locally after a crash and restart would themselves create a discoverable record subject to any applicable preservation obligation.
If you mean that remote workers are more likely to use Google Chat for sensitive information topics than in-person workers, yes, that could be an example of a peril of remote work. But, from the perspective of society rather than the company, making it harder for companies to hide misbehavior is actually an advantage of remote work.
Disclosure: I have worked for Google in the past, but not for more than 8 years now, and I have no inside knowledge of or connection to anything discussed in the submitted PDF.